Permeability of Rat Adrenals in vitro to D-Xylose in Presence and Absence of ACTH. ∗

Abstract

Summary

Studies on the permeability properties of bisected rat adrenals, incubated in vitro, have revealed marked differences from those which obtain in vivo. Thus, in absence of ACTH in vivo D-xylose is excluded from a major fraction of the cell water, but in vitro D-xylose rapidly penetrates and appears to equilibrate in about 70% of the cell water. In vivo, ACTH increases sugar distribution, but under in vitro circumstances, where a corticosteroidogenic response is observed, ACTH has no significant influence on rate of penetration or intracellular distribution of D-xylose. ACTH does, however, tend to increase inulin space of sectioned rat adrenal in vitro. While these findings suggest that the steroidogenic effect of ACTH in vitro is not dependent upon hormonal regulation of sugar availability, the possibility remains that an important aspect of ACTH action in vivo, where permeability barriers are operative, involves regulation of sugar permeability.